1. Field of the Invention
This invention relates to arc welding generally, and more particularly to a portable wirefeed arc welding system.
2. Description of the Prior Art
Conventional portable arc welding systems include a welding machine or power source (preferably a D.C. constant voltage type), a portable wire feeding unit with controls, and a welding gun or torch, with electrode power cables from the power source to the wire feeding and control unit and to the gun, a ground cable between the power source and the work, and contractor control and 110 or 115 volt A.C. supply cables between the power source and the portable control unit. The latter cables are hazardous and their maintenance is an important factor in efficiency, productivity and costs, especially in welding on bridges, ships, tanks, pipe lines, or other large structures. Consequently, elimination of those contactor control and 115 volt A.C. supply cables is very desirable.
That has been accomplished with the so-called arc voltage system by using a D.C. motor for the wirefeeder which operates from the low voltage in the welding current cable, but that requires the main contactor to be closed at all times which maintaines the welding cables and welding wire "hot." That is a very dangerous condition, and an accidental touching of the wire or gun tip to the work or surrounding grounded structure will cause instantaneous arcing and probable serious damage to the wirefeed system, such as a "burnback" of the wire into the gun tip, and possible burning of the operator's eyes if his protective helmet is not in place. Further, arcing on critical weldments not only leaves a cosmetic blemish, but also is metallurgically undesirable.